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NFS: add basic STATX_DIOALIGN and STATX_DIO_READ_ALIGN support 

NFS doesn't have DIO alignment constraints, so have NFS respond with
accommodating DIO alignment attributes (rather than plumb in GETATTR
support for STATX_DIOALIGN and STATX_DIO_READ_ALIGN).

The most coarse-grained dio_offset_align is the most accommodating
(e.g. PAGE_SIZE, in future larger may be supported).

Now that NFS has support, NFS reexport will now handle unaligned DIO
(NFSD's NFSD_IO_DIRECT support requires the underlying filesystem
support STATX_DIOALIGN and/or STATX_DIO_READ_ALIGN).

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
This commit is contained in:
Mike Snitzer 2025-09-19 10:36:31 -04:00 committed by Anna Schumaker
parent cda94457c2
commit 1f0d4ab0f5
1 changed files with 15 additions and 0 deletions
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15
fs/nfs/inode.c
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@ -1073,6 +1073,21 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
if (S_ISDIR(inode->i_mode))
stat->blksize = NFS_SERVER(inode)->dtsize;
stat->btime = NFS_I(inode)->btime;
/* Special handling for STATX_DIOALIGN and STATX_DIO_READ_ALIGN
* - NFS doesn't have DIO alignment constraints, avoid getting
* these DIO attrs from remote and just respond with most
* accommodating limits (so client will issue supported DIO).
* - this is unintuitive, but the most coarse-grained
* dio_offset_align is the most accommodating.
*/
if ((request_mask & (STATX_DIOALIGN | STATX_DIO_READ_ALIGN)) &&
S_ISREG(inode->i_mode)) {
stat->result_mask |= STATX_DIOALIGN | STATX_DIO_READ_ALIGN;
stat->dio_mem_align = 4; /* 4-byte alignment */
stat->dio_offset_align = PAGE_SIZE;
stat->dio_read_offset_align = stat->dio_offset_align;
}
out:
trace_nfs_getattr_exit(inode, err);
return err;